The function dlopen() loads the dynamic library file named by the null-terminated string filename and returns an opaque
"handle" for the dynamic library. If filename is NULL, then the returned handle is for the main program. If filename con‐
tains a slash ("/"), then it is interpreted as a (relative or absolute) pathname. Otherwise, the dynamic linker searches
for the library as follows (see ld.so(8) for further details):
o (ELF only) If the executable file for the calling program contains a DT_RPATH tag, and does not contain a DT_RUNPATH
tag, then the directories listed in the DT_RPATH tag are searched.
o If, at the time that the program was started, the environment variable LD_LIBRARY_PATH was defined to contain a colon-
separated list of directories, then these are searched. (As a security measure this variable is ignored for set-user-
ID and set-group-ID programs.)
o (ELF only) If the executable file for the calling program contains a DT_RUNPATH tag, then the directories listed in
that tag are searched.
o The cache file /etc/ld.so.cache (maintained by ldconfig(8)) is checked to see whether it contains an entry for file‐
o The directories /lib and /usr/lib are searched (in that order).